Method of and means for reducing electrical disturbances



D. G. M CAA Aug. 7, 1934.

METHOD AND MEANS FOR REDUCING ELECTRICAL DISTURBANCES 2Sheets-Sheet 1Filed Oct. 29, 1950 p in? a yz Aug. 7, I D. G MccAA 1,969,657

METHOD OF AND MEANS FOR REDUCING FILECTRICAL DISTURBANCES Filed Oct. 29,1950 2 Sheets-Sheet 2 Patented Aug. 7, 1934 PATENT OFFICE METHOD OF ANDMEANS FOR REDUCING ELECTRICAL DISTURBANCES David G. McCaa, Philadelphia,Pa.

Application October 29,

18 Claims.

The present invention relates to improvements in means for reducing andlimiting interfering pulsations in electrical circuits through whichelectrical energy is being transmitted in useful form and especially toapparatus and methods adapted to reduce the influence of atmosphericdevices originating externally of the device and is a continuation'inpart of the invention disclosed in my co-pending application, Serial No.

320,849,.filed Nov. 21, 1928, which, in turn, is a division of myapplication, Serial No. 74,087, filed Dec. 8, 1925, upon which PatentNo. 1,814,051 dated July 14, 1931 has issued. This application andco-pending application, Serial No. 492,054

.15 filed October 29, 1930, relate to the same generic invention, eachbeing intended to cover diiferent modifications thereof.

As is well known, when electrical disturbances are in evidenceduringradio-reception, they take 20 the form of audible noises whichoften completely submerge all other reproduced sounds. The origin ofsuch disturbances cannot be readily controlled nor their arrival at theantenna prevented. Hence the place where their effects may be decreasedis confined to thevicinity of the receiving system itself. To reduce orsubstantially eliminate the effects of the oscillations, by which suchdisturbances are produced, requires that such oscillations be so far aspossible nullified and one method of accomplishing this purpose is toreduce the ratio of the energy due to disturbing oscillations tothe'energy due to the desired or signal oscillations. It is, therefore,the object of the present invention to provide a method and apparatus sodesigned that the effects of electrical disturbances can be controlledand largely reduced without unduly affecting the quality of reception ofdesired signals, thus permitting the reception of signals with greatdeal more clarity and substantially as great intensity as when nodisturbances are present.

Another object is to provide an improved method and device fordifferentiating in electrical circuits between impulses of electricalenergy of different amplitudes, the higher amplitude waves being dampedas, for example, atmospheric static or other similarelectriddisturbances and the lower amplitude wave being the desiredsignal wave. l

. A further object of the invention is to provide a method and apparatusthat will enable the electrical disturbances to be divided intocomponents and so controlled that the divided com ponents oppose eachother in such a ratio that the components of the low amplitude: signalwaves 1930, Serial No. 492,052

will oppose each other to only a slight extent while the components ofthe high amplitude impulse waves will oppose each other to such anextent as to completely neutralize each other when the amplitude of saidhigh impulse waves is a maxi- 59 mum.

Another object of the invention is to provide a method and apparatus bywhich the effects of electrical disturbances may be substantiallyreduced to a point where they are no longer troublesome and which can beoperated in connection with an ordinary receiving system in either radioor telephone line communication. The apparatus in this respect,including appliances, may be disposed either between the receivingsystem and the input thereto or connected into the circuit of thereceiving system between the output of the system and the soundreproducing device or it may be applied directly to the soundreproducing device itself. l

Other objects and advantages of the invention will appear more fullyhereinafter from the following detailed description taken together withthe accompanying drawings, in which:

Fig. 1 is a schematic wiring diagram illustrating the basic arrangementfor carrying out my invention;

Fig. 2 is a diagram illustrating a specific embodiment for carrying outmy invention;

Fig. 3 is a graphic representation of the operation of the systemdisclosed in Fig. 2;

Fig. 4 is a modified embodiment of the syste of my invention;

Fig. 5 illustrates another embodiment in which the principle of theinvention is applied directly to an electrodynamic sound reproducer; and

Fig. 6 is a detail View of an electrodynamic sound reproducer showingthe relation of the energizing coils with respect to the acousticdiaphragm. V

Referring to Fig. 1, there is shown a system comprising two paths whichpresent to currents flowing therethrough impedances Z1 and Z2,respectively. Four transformers P, P, P and P couple the two paths tocommon input and out- 100 put circuitsthe secondary windingsoftransformers P1 and P1 being connected in opposition as indicated. Asource of wave energy G is connected in series with the primary windingsof transformers P and P. The output terminals X 105 and Y may beconnected to any circuit or translating device. Y

The impedance devices Z1. and Z2 each may have anyone of threepossiblecharacteristics. They may favor the undesirable high amplitude waves 110by presenting much less impedance to such waves than to low amplitudesignal waves. They may favor the low amplitude signal waves bypresenting much less impedance to them than the high amplitude waves, orthey may have a straight line characteristic favoring neither high norlow amplitude waves, the current merely being proportional to theapplied voltage. This will be more clear as the description proceeds.

Referring to Fig. 2, the terminals 1 and 2 may be connected to antennaand ground, respectively, or to any other source of signal energy. Atransformer 5 has its primary 6 connected to the terminals 1 and 2 andthe secondary 7 is connected to two paths comprising, in one caseresistance R and primary 9 of transformer 8 and, in the other case, twogroups, A and B, of rectifying devices 13 and 14 and another primary 10of transformer 8. The rectifier elements 13 of group A are arranged inopposed relation to the rectifier elements 14 of group B and, in thisinstance, are provided for use as asymmetrical impedance devices ratherthan as rectifiers. The primaries 9 and 10 of the transformer 8 arearranged in opposed relation so that the energy in the path includingthe resistance R opposes the energy in the path including the rectifyingelements 13 and 14. The secondary 11 of the transformer 8 is connectedto the output terminals 3 and 4. It will be noted that when the primary6 becomes energized, the corresppnding voltages are produced across thesecondary '1 and for one-half cycle of the incoming wave, for example,when the upper terminal of the secondary 7 is positive, current willflow through the junction point 7a where it divides, part of it goingthrough resistance R, primary 9 and back to the other terminal of thesecondary '7. The other portion of the current will flow from thejunction 7a through the rectifying elements 13, through primary 10 inopposed relation to the current in primary 9 and back to the transformersecondary 7. In the second half cycle of the wave, when the upperterminal of the secondary 7 is negative, current fiows through theresistance R and primary 9 as before except in the reverse direction andthe other portion of the circuit now flows through primary 10 inopposition to the current in primary 9, through the rectifying elements14 and back to the secondary '7. In this way, both halves of theincoming waves are acted upon.

Referring to Fig. 3, which graphically illustrates the relation of thecurrents in the paths of primaries 9 and 10 of Fig. 2, the curve IArepresents the current flowing through the rectifier elements 13 forvarious values of voltage E. The curve In is symmetrical with the curveIA and indicates the current passing through the rectifier elements 14and is illustrated in Fig. 3 below the voltage axis. The curve In, onthe other hand, is a straight line showing the linear variation ofcurrent when the voltage of the current is opposite to the currents ineither of the rectifiers, because of the opposed relation of thewindings 9 and 10. The path through the rectifiers then favors the highamplitude waves while the path through the resistance is impartial.

It will be noted that parts of the curves IA and In extend beyond theorigin in a negative direction from the origin and the resultant currentis illustrated by the curve IA+B.

To make clear the operation of the circuit of Fig. 2, the signal waveshave been shown as having a value s as compared to the high impulsewaves, such as atmospheric static, having a value c. It will be notedthat when the high impulse Waves have a value equal to c, the current inthe path of the rectifying elements is exactly equal but opposite to thecurrent in the path of the resistor R, as indicated by the points a anda respectively, the resultant output in secondary 11 being zero. If thevoltage of the high impulse wave is half the value as indicated by thepoint g, the resultant output in transformer 11 will be reduced to 50%of the input, as illustrated by the point h on the curve IA+B-IR. Forthe low amplitude signal waves, the voltage of which has been assumed tobe of a value c, the resultant output of secondary 11 is approximatelyof the input as illustrated by the point f on the curve IA+B IR. Itwill, therefore, be noted that the high impulse waves will besubstantially reduced or practically neutralized while the low amplitudesignal waves are permitted to pass through to the extent ofapproximately 80% or more. The same results are, of course, obtained onboth halves of the wave, as illustrated in the left portion of thediagram of Fig. 3.

The rectifying elements 13 and 14 may be carborundum crystals providedwith proper bias or may be rectifiers of the dry-contact ormetallicoxide type. The characteristic curves IA and In may be varied byvarying the contact pressure between the rectifier elements or varyingthe number of units for each of the groups A and B or varying the areaof contact between each pair of members of the rectifier elements. Theresistor R is made adjustable in order that the point a on the curve Inmay be adjusted to correspond to the point a on the curve IA+B forvarious values of the input voltage. By adjusting the rectifier elementsand the resistor R, the characteristics of each may be so modified thatthe reverse action may take place, that is, the low amplitude waves maybe made to substantially neutralize each other while the high amplitudeimpulses may be permitted to pass through the system. Furthermore thesystem illustrated in Fig. 2 may be operated either with terminals 1 and2 as the input and terminals 3 and 4 as the output or vice versa. Thesame results will be obtained in either case.

Fig. 4 illustrates a modification in which the input terminals 27 and 28are connected to a pair of primaries 31 and 32 connected in seriesopposed relation on the cores 33 and 34, respectively. In this instance,a secondary 35 is wound on the same core 33 with primary 31 and thesecondary 36 is wound on the same core 34.- with the primary 32.

The secondary 35 provides one path through a circuit including theprimary 31 which is wound on core 33 and secondary 36 provides a secondpath through a circuit including the primary 32' which is wound on acore 34. The secondaries 35 and 36' are wound on the same cores withprimaries 31 and 32' respectively and in series opposed relation to eachother as indicated by the arrows. They constitute the output circuit ofthe system and are connected to the output terminals 29 and 30. Twogroups of rectifiers A and B are connected in shunt relation withsecondary 35 and primary 31 while two similar groups A and B areconnected in series with secondary 36 and primary 32. The circuit ofsecondary 35 with groups A and B inshunt therewith ofiers a higherimpedance to high ampli-- tude impulses than the circuit of secondary 36which is in series with groups A and B. In

order that the relative gain of the output transr le formers may bevaried, windings 32" and 36 are arranged so that their coupling may bevaried,

as indicated by the arrow. The reason for this will appear presently.Obviously the gain of the output transformers may be varied in otherways, such as by means of tapped windings, potentiometers across thewindings, etc.

Ifwe assume that the path through rectifiers A and B favors signalcurrents over high amplitude currents in the ratio 2 to I, that the paththrough rectifiers A and B favors high amplitude currents over signalcurrents in theratio 2 to 1, and that transformer 3l'-35 has a stepupratio of 2 to 1, thecoupling of transformer 32'36 necessary to balanceout the high amplitude currents may be readily determined. For example,if the incoming wave comprises 10 units of signal waves and 40 units ofhigh impulse waves, then assuming that 5 units of signal waves and unitsof high impulse waves appear in primary 31, 10 units and unitsrespectively will appear in secondary 35. Now if 2%; and 20 unitsrespectively of signal and high amplitudewaves appear in primary 32',then the 'cou c pling of windings 3234' must be such that a ratio of 1to 1 is obtained, thus balancing out the high amplitude waves and givinga resultant of 7 units of signal waves in the output circuit.

In Fig. 5 is shown a modification in which a primary 39 is connected tothe input terminals 37 and 38 and is wound on a'core 40 with a secondary41 mounted on the same core. The output of the secondary is dividedinto-two paths in the samemanner as in Fig. 1 but, in this instance,

:5 the circuit is arranged to actuate an electrodynamic loud speakerhaving movable coils M1 and M2 which are adapted to actuate an acousticdiaphragm and are arranged in opposed relation similarly as theprimaries 9 and 10 in Fig. l and are connected so that the coil M1 is inthe path of resistor Rwhile the coil M2 is in the path of. the rectifiergroups A and B. The sound reproducer is provided with'the usual fieldcoil 46 energized by-a source of direct-current energy 47 and wound onthe pole piece 43 of a magnet 42 which is provided with additional polepieces 44 and 45 so that the like poles thereof are opposite each otherand the armature coils M1 and M2 are located therebetween.

Fig. 6 illustrates more clearly the arrangement of the coils Ml and M2to cooperate with the acoustic diaphragm 48 and shows schematically asection taken through the magnet 42 and through the armature coils M1,M2 and through the field coil46. In this instance, when the high impulsewaves are of sufiicient value to cause equal currents to flow throughcoils M1 and M2, they will be substantially neutralized and, therefore,produce no action on the diaphragm 48, whereas the low amplitude signalwaves will affect the diaphragm in proportion to their amplitudes asindicated on the curve IA+BIR.

It will be noted that the systems of the present applicationsdifferentiate from the systems dis- E closed in my c-o-pendingapplication Serial No.

320,849 hereinbefore mentioned in that the impedance in the pathprovided to discriminate against the low amplitude waves is of a finitevalue for waves of all amplitudes which may normally be introduced intothe path while the impedance of the corresponding path in the systems ofthe co-pending application becomes infinite for certain amplitudes.

While I have shown several modifications of my invention for purposes ofillustration and description and for explaining the operatingprinciples, other changes and modifications therein may be apparent tothose skiled in the art and I, therefore, desire to be limited only bythe scope of the appended claims.

I claim:

1. In a device for discriminating between electrical waves of a givenamplitude and impulse waves of a different amplitude, two electricalpaths operative with respect to the source of said waves, an impedancedevice associated with each of said paths, the impedance of the deviceof one of said paths adapted to vary in relation to the energy in saidpatir while the impedance of the other device remains constant, theimpedance of both of said devices being of finite values to all Wavesderived from said source, and a system assoeiatedwith both paths forcombining the energy from said paths.

2. In a device for discriminating between electrical waves of a givenamplitude and impulse waves of a diiierent amplitude, two electricalpaths operative with respect to the source of said waves, an impedancedevice in each of said paths, the impedance of the device of "one ofsaid paths varying in relation to the amount of energy associated withits path, while the impedance of the device of the other path remainssubstantially constant, the impedance of both of said devices being offinite values to all waves derived from said source, and a systemassociated with both paths for combining the waves of said paths inopposed relation.

3. In a device for discriminating between electrical waves of a givenamplitude and impulse waves of a different amplitude, two electricalpaths operative with respect to the source of said waves, one of whichhas associated therewith a symmetrical impedance device, the other ofwhich has associated therewith a pair of asymmetrical impedance devicesin reverse relation, and a system associated with both paths forcombining the energy of said paths.

4. In a device for discriminating between elec trical waves of a givenamplitude and impulse waves of a difierent amplitude, two electricalpaths operative with respect to the source of said waves, one of whichhas associated therewith a symmetrical impedance device, the' other ofwhich includes a group of asymmetrical impedance devices, and a systemassociated with both for combining the energy of said paths in opposedrelation.

5. In a device for discriminating between electrical waves of a givenamplitude and impulse waves of a diiierent amplitude two electricalpaths operative with respect to the source of said waves, one of whichincludes a symmetrical impedance device, the other of which includes apair of groups of asymmetrical impedance devices arranged so that onegroup operates on one-half cycle of said waves and the other group onthe other half cycle of said waves, and a system associated with bothpaths for combining the energy of said paths in opposed relation.

6. In a device for discriminating between electrical waves of a givenamplitude and impulse waves of a different amplitude, two electricalpaths operative with respect to the source of said waves, one of saidpaths including a resistor, the other of said paths including two groupsof rectifying devices arranged to operate on both halves of said waves,and an output circuit inductively related to both paths for combiningthe energy from said paths.

7. In a device for discriminating between electrical waves of a givenamplitude and impulse waves of a different amplitude, two electricalpaths operative with respect to the source of said waves, one of saidpaths including a resistor and a primary winding of a transformer, theother of said paths including two groups of rectifying elements arrangedto operate on both halves of said waves and a second primary of saidtransformer, said primaries being arranged so that the energy from saidpaths will be combined in the secondary of said transformer.

8. In a device for discriminating between elec trical waves of a givenamplitude and impulse waves of a different amplitude, two electricalpaths operative with respect to the source of said waves, one of saidpaths including a resistor and a primary winding of a transformer, theother of said paths including two groups of rectifying elements arrangedto operate on both halves of said waves and a mcond primary of saidtransformer, said primaries being arranged so that the energy from saidpaths will be combined in opposed relation in the secondary of saidtransformer.

9. In a device for discriminating between electrical waves of differentamplitudes, two electrical paths operative with respect to the source ofsaid waves, one of said paths including an impedance system associatedtherewith, the ratio of output to input of one path increasing as theinput Wave amplitude increases, and the ratio of output to input of theother path being at least as low for high amplitude input waves as forlow amplitude input waves.

10. In a device for discriminating between electrical waves of diiierentamplitudes, two electrical paths operative with respect to the source ofsaid waves, one of said paths including an impedance system associatedtherewith, the ratio of output to input of one path increasing as theinput wave amplitude increases, the ratio of output to input of theother path being at least as low for high amplitude input waves as forlow amplitude input waves, and a system associated with said paths forcombining the energy from said paths.

11. In a device for discriminating between electrical waves of difierentamplitudes, two electrical paths operative with respect to the source ofsaid waves, each of said paths including an impedance system associatedtherewith, the ratio of output to input of one path decreasing and ofthe other path increasing as the input wave amplitude increases.

12. In a device for discriminating between electrical waves of differentamplitudes, two electrical paths operative with respect to the source ofsaid waves, each of said paths including an impedance system associatedtherewith, the ratio of output to input of one path decreasing and ofthe other path increasing as the input wave amplitude increases, and asystem associated with said paths for combining the energy from saidpaths.

13. The method of discriminating between electrical waves of differentamplitudes which comprises dividing each wave into at least twoportions, operating upon one portion to produce increasing output toinput ratio thereof with increasing input wave amplitude, operating uponthe other portion to maintain the output to input ratio thereof at leastas low for high amplitude input waves as for low amplitude input waves,and recombining said portions so as to neutralize the effects of oneportion.

14. The method of discriminating between electrical waves of differentamplitudes, which comprises dividing each wave into at least twoportions, operating upon one portion to increase and upon the other todecrease the output to input ratio thereof with increasing input waveamplitude, and recombining said portions so as to neutralize the effectsof one portion.

15. In a device for separating desired from undesired oscillations, aplurality of coils in opposed relation, an output circuit operativelyassociated with said coils, a. symmetrical impedance device associatedwith one coil for causing it to present constant impedance to energytherein, and asymmetrical impedance devices associated with another coilfor varying the impedance thereof to energy therein, the impedance ofall of said devices being of finite values to all waves.

16. In a device for separating desired from undesired oscillations, aplurality of coils in opposed relation, an output circuit operativelyassociated with said coils, a symmetrical impedance device associatedwith one coil for causing it to present constant impedance to energytherein, and a pair of oppositely disposed asymmetrical devicesassociated with another coil for varying the impedance thereof to bothhalf cycles of energy waves therein, the impedance of all of saiddevices being of finite values to all waves.

17. In a device for separating desired from un desired oscillations, aplurality of coils in opposed relation, an output circuit operativelyassociated with said coils, a resistor associated with one coil forcausing it to present constant impedance to energy therein, and groupsof rectifying devices associated with another coil for varying theimpedance thereof to energy therein, the impedance of said resistor andof all of said devices being of finite values to all waves.

18. The method of separating desired from undesired oscillations whichcomprises operating a pair of coils in opposed relation to each other sothat one presents finite constant impedance to energy therein while theother presents finite varying impedance to energy therein.

DAVID G. MCCAA.

